This invention relates to a method and an apparatus for forming a rubber sheet having cords therein by coating a rubber material on both sides of a plurality of parallel cords.
Methods and apparatuses for forming rubber sheets having cords therein have been known as disclosed, for example, in PCT Publication No. WO 89/10,834. In the method disclosed in the Publication, a plurality of cords are supplied into circumferential grooves formed in the outer circumference of a forming roll on one side of its axial direction to arrange the cords with equal pitches. Thereafter, a first rubber sheet is pressure-joined with one side of the cords arranged with equal pitches in a first pressure-joining position between the forming roll and a pressure-joining roll. The cords joined on their one side with the first rubber sheet are then fed to a second pressure-joining position spaced a predetermined distance in the axial direction of the forming roll from the first pressure-joining position, during which the cords are twisted and turned through 180.degree.. Thereafter, a second rubber sheet having a rectangular cross-section is supplied into a second pressure-joining position between the forming roll and the pressure-joining roll so that first and second rubber sheets are pressure-joined with each other to form a rubber sheet having cords therein.
In the method of forming the rubber sheet having cords as above described, after the cords joined with the first rubber sheet have been moved away from the first pressure-joining position, the cords are fed to the second pressure-joining position spaced in the axial direction from the first pressure-joining position, while the cords are twisted and turned through 180.degree. by a plurality of guide rollers. Consequently, the cords joined with the first rubber sheet are considerably deformed during their movement from the first pressure-joining position to the second pressure-joining position. As a result, the pitches of the cords previously regulated in order by the circumferential grooves of the forming roll are unavoidably disturbed during the movement to the second pressure-joining position. Moreover, the cords in the second pressure-joining position are free from the restraint by the grooves of the roll, and rubber material of the second rubber sheet tends to flow in the axial directions of the forming roll when the first and second rubber sheets are being pressure-joined with each other. Therefore, cords are pulled by the flow of the rubber material so as to cause the pitches of the cords to be further disturbed.